Display Device and Control Method Therefor

2. The display device of claim 1, wherein after the second brightness decrease time elapses, the controller is further configured to control the display to return the brightness of the display from the second brightness value to a value different from the second brightness value based on the first signal being received at the settop box from the external device within the second prescribed time.

3. The display device of claim 1, wherein the controller is further configured to set a slope of the first brightness decrease time to be different from a slope of the second brightness decrease time.

5. The display device of claim 1, wherein based on the first signal not being received at the settop box from the external device within the second prescribed time, the controller is further configured to control the transceiver to transmit the first signal to the settop box.

6. The display device of claim 5, wherein the controller is further configured to control the transceiver to transmit the first signal to the settop box via High Definition Multimedia Interface-Consumer Electronics Control (HDMI-CEC) communication.

7. The display device of claim 5, wherein after the second brightness decrease time elapses, the controller is further configured to control the transceiver to transmit the first signal to the settop box based on the first signal not being received at the settop box from the external device within the second prescribed time.

8. The display device of claim 1, wherein based on a number of local regions satisfying a first condition and a second condition being equal to or greater than a prescribed number, the controller is further configured to determine at least the prescribed number of local regions of the whole display region as the fixed region, wherein the first condition is satisfied if an Average Picture Level (APL) of the local region is equal to or greater than a prescribed rate, and wherein the second condition is satisfied if an interval, in which an APL difference between a previous frame and a current frame of the local region is smaller than a first value, is equal to or greater than a prescribed time.

9. The display device of claim 1, wherein the controller is further configured to set one of the first brightness decrease time or the second brightness decrease time to a value corresponding to the default brightness.

11. The method of claim 10, further comprising, after the second brightness decrease time elapses, controlling the display to return the brightness of the display from the second brightness value to a value different from the second brightness value based on the first signal being received at the settop box from the external device within the second prescribed time.

12. The method of claim 10, further comprising setting a slope of the first brightness decrease time to be different from a slope of the second brightness decrease time.

14. The method of claim 10, further comprising, based on the first signal not being received at the settop box from the external device within the second prescribed time, controlling the transceiver of the display device to transmit the first signal to the settop box.

15. The method of claim 14, wherein controlling the transceiver to transmit the first signal to the settop box comprises controlling the transceiver to transmit the first signal to the settop box via High Definition Multimedia Interface-Consumer Electronics Control (HDMI-CEC) communication.

16. The method of claim 14, further comprising, after the second brightness decrease time elapses, controlling the transceiver to transmit the first signal to the settop box based on the first signal not being received at the settop box from the external device within the second prescribed time.

18. The method of claim 10, further comprising setting one of the first brightness decrease time or the second brightness decrease time to a value corresponding to the default brightness.